Threefold error in the reported zero-field cooled magnetic moment of single crystal $La_2SmNi_2O_7$

Abstract

For a relatively long time, the observation of the DC diamagnetic state in highly compressed nickelate superconductors [1],[2] has been a challenging experimental problem. And recently Li et al.[3] reported on the measurements of the DC diamagnetism in zero-field-cooled (ZFC) and field-cooled (FC) pressurized single crystal $La_2SmNi_2O_7$. From the analysis of experimental data, Li et al.[3] reported that the superconducting phase fraction in their $La_2SmNi_2O_7$ sample measured in the ZFC mode is 62.1%, and the superconducting phase fraction in the FC mode is 14.4%. It should be clarified that we regard the measurements of the DC diamagnetic state [3] in $La_2SmNi_2O_7$ (and more recently in $Pr_4Ni_3O_{10}$ [4]) as outstanding experimental results confirming bulk superconductivity in pressurized nickelates. However, we should note that Li et al.[3] made a threefold error in their calculations of the superconducting phase fraction in $La_2SmNi_2O_7$. We believe that correcting this and other errors in Ref.[3] will benefit the physics community.